code: def test_call(lut):
      n_values = 10
      arr = lut(np.linspace(0, 1, n_values))
      assert isinstance(arr, np.ndarray)
      assert arr.shape[0] == n_values
  
      assert lut.map_value(0.5) == lut.map_value(0.5)
  
imports: import numpy
  import pytest
  import vtk
  import pyvista
  from pyvista import Color, LookupTable
label_desc: Use image node_id 24 for calling a global function with example usage: test_call(lut) without return types